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981.
B. A. Tertov Yu. G. Bogachev Yu. V. Koshchienko G. M. Suvorova E. B. Tsupak N. K. Chub S. F. Breus 《Chemistry of Heterocyclic Compounds》1986,22(8):868-872
Organolithium and organosodium compounds of 1,2-dimethyl-, 1-methyl-2-ethyl-, 1-methyl-2-propyl-, and 1-phenyl-2-methylbenzimidazole, containing the metal in the alkyl group at position C(2), were obtained by metallation. It was found that metallation can be complicated by the addition of the metalling reagent at the C=N bond of the heterocycle. It was shown that the obtained organometallic compounds can be used for the synthesis of various derivatives of benzimidazole.The calculation was performed with the standard bond lengths. A planar model was used for the carbanion.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1073–1077, August, 1986. 相似文献
982.
Abstract— Murine cytomegalovirus, a herpes virus, was used as a model virus to investigate the mechanism of the anti-viral action of phenylheptatriyne in long wave ultraviolet light. The genome and proteins of the inactivated virus penetrated the nuclei of susceptible cells normally. Furthermore, the viral genome did not contain extra single strand breaks or cross-links. However, cells infected with the treated virus did not synthesize late viral proteins, as determined by polyacrylamide gel electrophoresis. nor did they synthesize late viral RNA and viral DNA according to nucleic acid hybridization tests. Thus the compound may interfere with an early viral function so that the replication cycle cannot proceed. 相似文献
983.
984.
V. V. Rossikhin E. O. Voronkov Yu. A. Kruglyak 《International journal of quantum chemistry》1980,17(2):327-338
The quantum-mechanical virial theorem (in diagonal and nondiagonal forms) for molecules in an external, weak, uniform electric field is used for obtaining the analytical expression of the potentialenergy surface in the Hartree–Fock–Roothaan one-determinantal approximation. The polarizability tensor components of the H2O molecule are computed on this basis. The dependence of basing the atomic orbitals upon the intensity of the applied field lead to good coincidence of results with the data of near Hartree–Fock calculations. 相似文献
985.
Very low pressure photolysis (VLPØ) of chlorine nitrate was performed in a quartz Knudsen cell. The light source was a 2500 W high-pressure xenon lamp, and a modulated molecular-beam mass spectrometer was used to monitor the concentration of ClONO2 and photolysis products. Because of the low pressures used (? 10?3 torr) and the short residence time in the cell (≈1 s), secondary reactions were unimportant and the primary products could be directly identified. The primary photolysis products (λ ≈ 2700 Å) are atomic chlorine and NO3 free radical. Chlorine atoms were identified both by the appearance of Cl2 (wall recombination product; the walls were not poisoned) and by HCl produced when C2H6 was added to the cell. Nitrate free radical was directly identified as a mass peak at m/e = 62, as well as by chemical titration with nitric oxide: NO3 + NO → 2NO2. It was verified by direct tests that the peak at m/e = 62 did not arise from possible HNO3 contamination or from N2O5, a possible secondary product. This titration reaction was used to measure quantitatively a lower limit to the primary quantum yield, φ ? 0.5 ± 0.3. This represents a lower limit because of the unknown extent of the secondary photolysis of NO3 under our conditions. We believe this to be the first observation using mass spectrometry of the NO3 free radical. The quantum yield for atomic chlorine is φ = 1.0 ± 0.2. N2O was used to test for O(1D) according to the reaction, O(1D) + N2O → products; none was observed. Triplet oxygen, O(3P) was observed to the extent of ≈ 10% by the reaction O(3P) + NO2 → NO + O2, but this yield can also be due to the photolysis of NO3 free radical produced in the primary step. We conclude that the predominant reaction pathway is . 相似文献
986.
The silicate compounds Sc2Si2O7 and In2Si2O7 have been converted from thortveitite type to pyrochlore type at 1000°C, 120 kbar, with resulting cell constants of 9.287(3) and 9.413(3) Å, respectively. Invariant reflection intensities in the X-ray powder diffraction patterns allowed precise absorption corrections to be made, and refinement of thermal parameters and of the single structural parameter x gave values of 0.4313(21) and 0.4272(15), respectively. The corresponding six-coordinate SiO distances were 1.761(7) and 1.800(5) Å, and the average eight-coordinate distances for ScO8 and InO8 were 2.267 and 2.275 Å. Values of structure-refined bond lengths for compounds containing six-coordinate silicon are surveyed, and overall weighted average octahedral distances of 1.782(14) Å for SiO and 2.520(18) Å for OO are derived. Pyrochlore phases were not produced from rare-earth disilicate or monosilicate phases subjected to the same reaction conditions as the Sc and In compounds. 相似文献
987.
I. M. Ovcharova E. S. Chaman E. S. Golovchinskaya 《Chemistry of Heterocyclic Compounds》1967,3(6):876-876
We have synthesized a group of new 8-substituted 1, 7-dimethylxanthines which are of interest for biological investigation as very close structural analogs of some 8-substituted theobromine derivatives obtained previously. In particular, we have carried out the conversion of 8-hydroxymethyl-1, 7-dimethlxanthine (I) [1] into 8-chloromethyl-1, 7-dimethylxanthine (II) and from this, by heating it for 6 hours with an excess of diethylamine or by condensing it with sodioacetylaminomalonic ester in ethanol we have obtained 8-diethylaminomethyl-1, 7-dimethylxanthine (III) and its hydrochloride (compare [2]) or 8-(-acetylamino-, -diethoxycarbonylethyl)-1, 7-dimethylxanthine (IV). The hydrolytic cleavage of the latter, accompanied by partial decarboxylation, led to 1, 7-dimethyl-8-xanthinylalanine (V) (cf. [3]). 相似文献
988.
A procedure is described for the titrimetric determination, of arsenic and antimony without separation. Total combined arsenic and antimony were determined by reduction with tin(II) chloride and titration with permanganate; antimony is found by selective reduction with mercury(I) chloride and titration with permanganate. A precision of 0.1–0.2% was obtained for total combined arsenic and antimony, and approximately 1% for antimony alone (small amounts in the presence of large amounts of arsenic). The procedure was developed for and applied to the analysis of synthesized compounds of the type MnAs1-xPx and MnAs1-ySby. 相似文献
989.
V. N. Shibaev Yu. Yu. Kosov I. V. Komlev E. I. Budovskii N. K. Kochetkov 《Russian Chemical Bulletin》1969,18(11):2350-2356
Conclusions We synthesized two analogs of the natural coenzyme adenosine diphosphate glucose: N6-methyl-ADPG and N6, N6-dimethyl-ADPG.For communication 11, see [1].The following abbreviations are used in this article: ADPG) adenosine-5'-diphosphate-a-D-glucopyranose; N6-methyl-ADPG) N6-methylamino-9--D-ribofuranosylpurine-5-diphosphate--D-glucopyranose; N6, N6-dimethyl-ADPG) N6, Ng-dimethylamino-9--D-ribofuranosylpurine-5-diphosphate--D-glucopyranose.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2514–2521, November, 1969. 相似文献
990.
Summary Coagulation and reversal of charge effects of freshly prepared and heated solutions of hafnium tetrachloride have been studied as a function of the pH using aged silver halide sols and solsin statu nascendi. It was shown that the critical coagulation concentration and the critical stabilization concentration (due to charge reversal) increased with increasing pH. These observations have been related to the hydrolysis of the hafnium ion. At pH values above 4 essentially the entire amount of hafnium is present in the form of the neutral soluble, species Hf(OH)4. This accounts for the inability of the hafnium solutions to reverse the charge of the sols at higher pH values. The adsorption measurements carried out with the aid of the radioactive isotope181Hf showed that the neutral hydrolyzed species are strongly adsorbed on negatively charged silver iodide particles. The adsorbed amounts of hafnium on a AgI sol are considerably larger than in the case of charged hydrolyzed ions (such as hydrolyzed thorium ions) on a similar sol. This is explained by the ability of the neutral hafnium species, Hf(OH)4. to form a close-packed adsorbed layer. The results confirm previous findings that the enhanced adsorption of hydrolyzed ions is caused by the presence of the hydroxyl group, whereas the ionic charge plays a negligible role in this case.
Supported by the U.S. Army Research Office (Durham), Grant No. DA-ARO (D)-31-124-G 656.
Part of a PhD Thesis byL. J. Stryker, supported by a NASA Traineeship. 相似文献
Zusammenfassung Die Koagulations- und Umladungserscheinungen von frisch dargestellten und durch Erwärmung gealterten Lösungen von Hafniumchlorid wurden an Silberhalogenid-Solen in der Abhängigkeit vom pH untersucht. Es wurde festgestellt, daß die kritische Koagulationskonzentration und die kritische Stabilisationskonzentration (die Umladungsgrenze) mit steigendem pH höher werden. Diese Beobachtungen wurden durch die Hydrolyse des Hafnium-Ions erklärt. Wenn pH>4 ist, bestcht nahezu die ganze Menge von Hafnium als neutrale, gelöste Hf(OH)4 Moleküle. Damit wird es erklärt, daß die Silberhalogenid-Teilchen bei höheren pH-Werten durch Hafniumsalze nicht umgeladen werden können. Die mittels des radioaktiven Isotopen181Hf durchgeführten Messungen zeigten, daß die neutralen Hf(OH)4 — Moleküle stark an den negativ geladenen Silberjodid-Teilchen adsorbiert sind. Die adsorbierte Menge per Mol von AgI ist beträchtlich größer als die Menge der geladenen, hydrolysierten Ionen (wie z. B. ThOH3+), die an dem gleichen Sol bestimmt wurde. Dieser Effekt ist leicht erklärt, da man mit den neutralen adsorbierten Molekülen eine fest gepackte Adsorptionsschicht bilden kann. Diese Resultate bestätigen die früheren Befindungen, daß die höhere Adsorptionsfähigkeit der hydrolysierten Ionen durch die Hydroxylgruppe verursacht wird, während die Ionenladung eine zu vernachlässigende Rolle spielt.
Supported by the U.S. Army Research Office (Durham), Grant No. DA-ARO (D)-31-124-G 656.
Part of a PhD Thesis byL. J. Stryker, supported by a NASA Traineeship. 相似文献